Hydraulic control system for auxiliary power source

ABSTRACT

A hydraulic control system includes a variable displacement hydraulic pump, the pump having an inlet for receiving fluid, an outlet for discharging fluid under pressure, and a pump displacement input, a hydraulic motor having an inlet and an outlet a fluid circuit including a supply conduit for conducting fluid discharged by the pump to the motor and a return conduit for returning fluid discharged by the motor to the pump, a pump displacement control cooperating with the pump displacement input in order to vary a displacement of the pump, a control circuit in communication with the pump displacement control for controlling the pump output such that the motor is driven at a constant rotational speed and at least two valves controlling a rotational speed of the motor, wherein one of the valves provides coarser flow control resolution and another of the valves provides finer flow control resolution.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to hydraulic systems and, moreparticularly to, a hydraulic control system for an auxiliary powersource.

2. Description of the Related Art

Most engine driven vehicles utilize an internal combustion engine as aprimary power source for propelling the vehicle. However, numerousmodules and devices for the vehicle as well as the engine requireelectrical power. Typically, a rechargeable battery is provided with thevehicle as a basic power supply. The battery provides direct current(DC) electrical power for starting the engine and for operating certainDC compatible electrical loads when the vehicle is not running. Thebattery is recharged to maintain power by an alternator coupled to anddriven by the engine when the vehicle is running. Concurrently, thealternator also provides DC electrical power to the electrical loads ofthe vehicle.

With the advent of electronics in today's modern vehicle, groundvehicles, boats, and aircraft alike, the amount of electrical loadswhich require power has significantly increased. Moreover, many variousauxiliary electrical loads are dependent upon stable alternating current(AC), for example, rescue and military vehicles having AC poweredcommunications equipment. Additionally, many other vehicles, such asutility and telephone company repair and maintenance vehicles andvehicles providing electrical welding equipment, are increasinglyutilizing AC equipment dependent upon clean AC power.

Various systems have been proposed for alleviating the complication ofoperating both AC and DC powered electrical equipment. One such systeminvolves driving an auxiliary AC generator from the engine or principalpower plant of the vehicle. This can be accomplished by connecting thegenerator to a power take off or to any other suitable connection to anoutput of the engine. While this will indeed operate a generator,variations in engine speed will wreak havoc with characteristics ofpower output and therefore with equipment which is dependent upon stablevoltage and frequency characteristics of electrical power.

Accordingly, various systems have been proposed to control speed of theAC generator. One such system utilizes a hydraulic circuit having avalve for supplying a constant rate of fluid flow to a hydraulic motor.The hydraulic motor in turn drives the generator for supplying AC powerto certain AC compatible electrical loads. However, such systems canhave difficulty maintaining precise frequency output for controlling themost sensitive AC equipment and are often susceptible to prematuremechanical failure. Therefore, there is a need in the art to provide anew hydraulic control system for an auxiliary power source.

SUMMARY OF THE INVENTION

It is one object of the present invention to provide a hydraulic controlsystem for generating precise electrical output characteristics,particularly frequency and voltage output, along with prolonging life ofthe system, thus reducing warranty returns and costs associatedtherewith.

Accordingly, the present invention provides a hydraulic control systemincluding a variable displacement hydraulic pump drivably connectable toa primary power source, the pump having an inlet for receiving fluid, anoutlet for discharging fluid under pressure, and a pump displacementinput. The hydraulic control system also includes a hydraulic motorhaving an inlet for receiving fluid under pressure and an outlet fordischarging spent fluid, the motor being drivably connectable to anauxiliary power source. The hydraulic control system includes a fluidcircuit having a supply conduit for conducting fluid discharged by thepump to the motor and a return conduit for returning fluid discharged bythe motor to the pump and a pump displacement control cooperating withthe pump displacement input in order to vary a displacement of the pump.The hydraulic control system also includes a control circuit incommunication with the pump displacement control for controlling thepump output such that the motor is driven at a constant rotational speedto thereby drive the auxiliary power source at a constant rotationalspeed despite fluctuations in rotational speed of the primary powersource. The hydraulic control system further includes at least twovalves controlling a rotational speed of the motor, wherein one of thevalves provides coarser flow control resolution and another of thevalves provides finer flow control resolution.

In addition, the present invention provides a hydraulic control systemincluding a variable displacement hydraulic pump drivably connectable toa primary power source, the pump having an inlet for receiving fluid, anoutlet for discharging fluid under pressure, and a pump displacementinput. The hydraulic control system also includes a hydraulic motorhaving an inlet for receiving fluid under pressure and an outlet fordischarging spent fluid, the motor being drivably connectable to anauxiliary power source, a fluid circuit including a supply conduit forconducting fluid discharged by the pump to the motor and a returnconduit for returning fluid discharged by the motor to the pump, and apump displacement control cooperating with the pump displacement inputin order to vary the displacement of the pump. The hydraulic controlsystem further includes a control circuit in communication with the pumpdisplacement control for controlling the pump output such that the motoris driven at a constant rotational speed to thereby drive the auxiliarypower source at a constant rotational speed despite fluctuations inrotational speed of the primary power source. The hydraulic controlsystem includes an interface module having a display in communicationwith the control circuit for displaying real time system operatingcharacteristics to an operator and a wireless communication connectionbetween the display device and the control circuit.

One advantage of the present invention is that a new hydraulic controlsystem is provided for a vehicle that generates precise electricaloutput characteristics, particularly frequency and voltage output, basedon better flow control resolution. Another advantage of the presentinvention is that the hydraulic control system includes finer resolutioncontrol of the hydraulic fluid flow to the hydraulic motor, therebyenhancing flow capabilities. Yet another advantage of the presentinvention is that the hydraulic control system includes at least twovalves controlling the hydraulic fluid flow to the motor to perform overa wider range of flow variation. Still another advantage of the presentinvention is that the hydraulic control system includes an operatorinterface module to perform routine tasks or monitor information via awireless connection. Still another advantage of the present invention isthat the hydraulic control system may include a personal computer ormobile device applications to perform the same functions as the operatorinterface module.

Other features and advantages of the present invention will be readilyappreciated, as the same becomes better understood, after reading thesubsequent description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a hydraulic control system.

FIG. 1b is a schematic view of a hydraulic control system, according toanother embodiment of the present invention.

FIG. 2 is a schematic view of a control circuit for the hydrauliccontrol system of FIG. 1.

FIG. 2a is a schematic view of a control circuit, according to oneembodiment of the present invention, for the hydraulic control system ofFIG. 1 a.

FIG. 3 is a schematic view of another embodiment of the hydrauliccontrol system of FIG. 1.

FIG. 4 is a graph generally displaying system characteristics duringcold start operation for the hydraulic control system of FIG. 1.

FIG. 5 is a schematic view of yet another embodiment of the hydrauliccontrol system of FIG. 1.

FIG. 6 is a perspective view of an auxiliary module unit suitable formounting a hydraulic driven generator to an exterior of a vehicle.

FIG. 7 is a perspective view of an auxiliary module unit having afold-out cooler and being suitable for submersion.

FIG. 8 is a perspective view of the auxiliary module unit shown in FIG.6 with a serially connected secondary auxiliary power source in the formof a pump for hydraulic extraction equipment.

FIG. 9 is a schematic view of still another embodiment of the hydrauliccontrol system of FIG. 1.

FIG. 10 is a schematic view of a further embodiment of the hydrauliccontrol system of FIG. 1.

FIG. 11 is a schematic view of a yet further embodiment of the hydrauliccontrol system of FIG. 1.

FIG. 12 is a schematic view of a still further embodiment of thehydraulic control system of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring to the drawings, one embodiment of a hydraulic control system10 is illustrated in FIGS. 1 and 2. The hydraulic control system 10includes a hydraulic circuit 12 in FIG. 1 and a control circuit 14 inFIG. 2. As illustrated in FIG. 1, the hydraulic circuit 12 includes ahydraulic pump 16 to power the hydraulic circuit 12. The hydraulic pump16 has an inlet 18 for receiving fluid for pumping and an outlet 20 fordischarging pumped fluid under pressure. In one embodiment, thehydraulic pump 16 can be a variable displacement type pump, a fixeddisplacement type pump, or the like, for pumping pressurized fluidthroughout a fluid circuit 22. In one embodiment, the hydraulic pump 16can be driven by a primary power source 24, such as a vehicle powertake-off (PTO), belt drive, gasoline engine, diesel engine, or anysimilar input. The hydraulic pump 16 can include a thru-drive so that anadditional hydraulic pump or other auxiliary power device can beimplemented mechanically in series with the pump 16. It should beappreciated that a vehicle with a hydraulic pump (e.g., garbage truck,fire rescue vehicle, etc.) can be used to provide pressure in ahydraulic control system 10 containing one or more hydraulic circuits 12on the vehicle. It should also be appreciated that control of eachhydraulic circuit 12 can be implemented in a control block, ordistribution manifold, where fluid circuits 22 are enabled throughcontrol of electro-hydraulic or manual valve assemblies. It shouldfurther be appreciated that each hydraulic circuit 12 can then drive adesired hydraulic load (e.g., cylinders, fans, air pumps, hydraulicmotors) or external auxiliary connections which are made via hoses andfittings to an external load.

The hydraulic circuit 12 also includes a hydraulic motor 26, having aninlet 28 for receiving fluid under pressure and an outlet 30 fordischarging spent fluid. In one embodiment, the hydraulic motor 26 canalso be an external load connected via hoses and fittings to adistribution block and thus able to be attached to or removed from thevehicle and vehicle hydraulic control system 10 as desired. Thehydraulic motor 26 drives an auxiliary power source 32, which provideselectrical or mechanical power to loads or devices (not shown) of thevehicle. For example, the auxiliary power source 32 can be an ACgenerator, a mechanical drive system, or other source requiring constantrotational speed. Additionally, an electronic inverter or converter (notshown) can be added to the output of the auxiliary power source 32 tocreate a secondary power output type or to create two or more outputtypes simultaneously. In one embodiment, the hydraulic motor 26 can bedrivably connected to the auxiliary power source 32 through a shaft 34(as shown in FIGS. 1 and 2) or a belt or other means of powertransmission (not illustrated). In one embodiment, the hydraulic motor26 can be a fixed displacement gear type motor, vane type motor, pistontype motor, or the like.

The hydraulic control system 10 may contain a switch or multipleswitches (not shown) to select the electrical output. The switch orswitches may be mechanically or electrically actuated and be capable ofselecting various voltages, frequencies, or power types such as AC toDC.

The fluid circuit 22 includes a supply conduit 36, a return conduit 38,and a bypass conduit 40. The conduits 36, 38, and 40 can utilize quickdisconnect hydraulic fittings to aid in quick installation or removal ofany applicable component, or when connected as an external load to thehydraulic control system 10. The supply conduit 36 can be divided intoat least two sections—a valve supply conduit 36 a and a motor supplyconduit 36 b. The supply conduit 36 conducts fluid discharged by thepump 16 to the motor 26, while the return conduit 38 returns fluiddischarged by the motor 26 to the pump 16. The bypass conduit 40conducts fluid discharged by the pump 16 directly to the return conduit38, bypassing the motor 26, where the fluid is subsequently returned tothe pump 16.

In one embodiment, the hydraulic control system 10 includes a controlvalve assembly 42, such as an electro-hydraulic control valve assembly,disposed within the hydraulic circuit 12 and controlled by a systemcontroller 44 (shown in FIG. 2) of the control circuit 14. The controlvalve assembly 42 can be disposed serially and/or parallel with respectto the supply conduit 36 such that valve assembly 42 is interposedbetween the outlet 20 of the pump 16 and the inlet 28 of the motor 26.The control valve assembly 42 may include a housing 46 generallyenclosing a valve chamber 48. The control valve assembly 42 alsoincludes a valve 50 disposed within the valve chamber 48, which shuttlesback and forth between an opened position and a closed position. Thecontrol valve assembly 42 further includes a first fluid passage 52(shown in FIG. 3) and a second fluid passage 54. The first fluid passage52 is in fluid communication with the valve chamber 48 and the motorsupply conduit 36 b, while the second fluid passage 54 is in fluidcommunication with the valve chamber 48 and the bypass conduit 40. Thecontrol valve assembly 42 includes a solenoid 56 or other electronic orelectro-mechanical device drivably connected to the valve 50 forselectively moving the valve 50 incrementally within the valve chamber48 between the opened and closed positions. In one embodiment, thesolenoid 56 may be in electrical communication with the systemcontroller 44, which drives the solenoid 56. It should be appreciatedthat the system controller 44 can communicate with the control valveassembly 42 such that the valve 50 selectively closes and opens thefirst fluid passage 52 and the second fluid passage 54, thereby dividingfluid flow proportionally therebetween.

As the valve 50 divides the flow of hydraulic fluid between the firstfluid passage 52 and the second fluid passage 54, the fluid can becorrespondingly directed to the motor supply conduit 36 b and the bypassconduit 40, respectively. Fluid directed to the motor supply conduit 36b may be supplied to, and discharged by, the motor 26 for powering theauxiliary power source 32 before returning to the pump 16 via the returnconduit 38. Fluid directed to the bypass conduit 40 can bypass the motor26 completely as it is steered immediately to the return conduit 38,without being supplied to the motor 26, for restoring to the pump 16.

Referring to FIG. 1 a, one embodiment of a hydraulic control system 10,according to the present invention, is shown Like parts of the hydrauliccontrol system 10 of FIG. 1 have like reference numerals for thehydraulic control system 10 of FIG. 1A. The hydraulic control system 10of the present invention achieves enhanced flow capabilities byincluding finer resolution control of the hydraulic fluid flow to thehydraulic motor 26 and has the ability to perform over a wider range offlow variation. As illustrated in FIG. 1 a, the hydraulic control system10 includes at least two valves 50 disposed between the valve supplyconduit 36 a and the motor supply conduit 36 b. The valves 50 include afirst valve 50 a and a second valve 50 b disposed in parallel with thefirst valve 50 a. In order to increase resolution of control of thehydraulic fluid flow, the second valve 50 b can be smaller than thefirst valve 50 a, thus making the control range of the second valve 50 bsmaller. The first valve 50 a can then be used to provide the majorityof the hydraulic fluid flow to the hydraulic motor 26 and makeproportionally larger adjustments in the hydraulic fluid flow, keepingthe control range of the second valve 50 b where desired for fineadjustment to the actual desired hydraulic fluid flow rate for thehydraulic motor 26. The internal connections of the valves 50 a and 50 bin FIG. 1a are represented generically as a standard hydraulic valve. Inone embodiment, the valves 50 a and 50 b are proportional valves. Itshould be appreciated that the internal details of the valves 50 a and50 b may have slight depiction differences.

As illustrated in FIGS. 1 and 1 a, optionally, the hydraulic circuit 12may include a fluid reservoir 58 and a pump case drain 60 disposed atthe pump 16, a motor case drain 62 disposed at the motor 26, or both.The drains 60 and 62 can utilize quick disconnect hydraulic fittings toaid in quick installation or removal of any applicable component. Thefluid reservoir 58 can be in fluid communication with the fluid circuit22 and maintains hydraulic fluid on reserve that can be introduced tothe pump 16 via the return conduit 38. In one embodiment, possible casedrain flow from the pump 16 and the motor 26 can be directed back to thefluid reservoir 58 through drain conduits 64 a-b (as illustrated in FIG.3). Fluid flow in the return conduit 38 can be directed through aventuri boost 66, where fluid from the fluid reservoir 58 may be drawninto the return conduit 38 to replace that lost from the case drainflow, and supplied back to the pump 16. In another embodiment, asecondary pump or charge pump 16 b (FIG. 1b ) can be used where fluidfrom the fluid reservoir 58 may be pumped to the return conduit 38 toreplace that lost from the case drain flow and supplied back to the pump16. In one embodiment, the secondary pump is driven via a thru-driveoperation on the pump 16 but, in another embodiment, the secondary pumpcould be driven by any auxiliary power source. Finally, the drainconduits 64 a-b can be disposed in the fluid circuit 22 such that casedrain flow can be pulled directly to the return conduit 38 by theventuri boost 66, without first being directed to the fluid reservoir58.

Additionally, the hydraulic circuit 12 may also include a fluid filter68 and a fluid cooler 70. The fluid filter 68 and the fluid cooler 70are disposed serially and/or parallel with respect to return conduit 38.However, it should be appreciated that the fluid filter 68 and the fluidcooler 70 can be disposed anywhere within the fluid circuit 22.Impurities introduced into the hydraulic fluid as it gets cycled throughthe fluid circuit 22 can be filtered by the fluid filter 68. The fluidcooler 70, on the other hand, can cool fluid that passes therethrough.Accordingly, the fluid cooler 70 may include a heat exchanger (notseparately shown) for dissipating heat to ambient air, an electricallyor hydraulically operated fan 72 disposed adjacent the heat exchangerfor forcing ambient air through the heat exchanger, and a thermostat 74(FIG. 2) which controls operation of the fan 72 when fluid containedwithin the fluid cooler 70 exceeds a predetermined temperature. In oneembodiment, the thermostat 74 can directly control the fan 72, or, inanother embodiment, the thermostat 74 can control operation of the fan72 through the system controller 44. For example, the thermostat 74 andthe fan 72 may be in electrical communication with the system controller44. It should be appreciated that the system controller 44 may receivetemperature readings of the fluid in the fluid cooler 70 from thethermostat 74 and operate the fan 72 by transmitting a fan controlsignal 76 to the fan 72 when fluid contained within the fluid cooler 70exceeds the predetermined temperature.

The hydraulic control system 10 may also include a pressure sensor 78 a,a temperature sensor 78 b, a fluid level sensor 78 c, an electricaloutput 78 d (FIG. 2 only), a speed sensor 78 e, and an air temperaturesensor (not shown), collectively referred to as system control sensors78. Each system control sensor 78 can be provided as part of the controlcircuit 14, shown in FIG. 2, and are configured to provide controlinputs to the system controller 44. The system control sensors 78 can bedeployed throughout the hydraulic control system 10 to measure systemvitals and assure the auxiliary power source 32 is driven at constantspeeds.

Referring again to FIGS. 1 and 1 a, the pressure sensor 78 a can bedisposed along the valve supply conduit 36 a proximate the pump 16 tosense hydraulic pressure. However, it should be appreciated that thereare many other locations in the fluid circuit 22 for positioning thepressure sensor 78 a so long as it can accurately sense that the pump 16is operating. Similarly, the temperature sensor 78 b can be disposedalong the fluid circuit 22 to monitor hydraulic fluid temperature. Inone embodiment, the temperature sensor 78 b can be separate from thethermostat 74 and thus provide a separate input to the system controller44, or, in another embodiment, the temperature sensor 78 b can be thesame as the thermostat 74. The fluid level sensor 78 c can be disposedwithin the fluid reservoir 58 to monitor the level of hydraulic fluidwithin the reservoir 58. If the fluid level becomes low, the systemcontroller 44 may announce a tell-tale alarm to the operator. If thefluid level becomes extremely low, the system controller 44 may causethe hydraulic control system 10 to shut down entirely to prevent damageto the pump 16. It should be appreciated that the temperature sensor 78b can be disposed in close proximity to the auxiliary power source 32.

In one embodiment, the auxiliary power source 32 can be an AC generator.Accordingly, the electrical output 78 d can be a current sensor, voltagesensor, or both for monitoring the generator's operatingcharacteristics, including current, voltage, and frequency. Asillustrated in FIG. 2, the electrical output 78 d can be connected tooutput conductors 80 of the auxiliary power source 32 to sense theoperating parameters of the auxiliary power source 32. In anotherembodiment, the speed sensor 78 e may be provided to monitor rotationalspeed of the motor 26 and the shaft 34, by sensing each revolution ofthe shaft 34, in order to provide controlled input to the systemcontroller 44 relating to operation of the motor 26.

Additional embodiments can consist of the auxiliary power source 32being any device that requires or prefers a constant RPM. These devicescan be connected serially to provide a constant RPM for multiple devicesor individually. In one embodiment, a clutch or otherconnection/disconnection method may be used to actuate or deactivate aparticular device. In another embodiment, hydraulic valving could allowfor the use of multiple devices with independent control, and additionalexternal hydraulic circuits. These devices can include, but are notlimited to, hydraulic pumps such as for extraction tools, air pumps suchas for filling breathing apparatus tanks, and foam pumps such as forpressurizing the suppression foaming equipment.

Referring now to FIG. 2, the control circuit 14 will be described infurther detail with reference to an AC generator as the auxiliary powersource 32, although other applications referred to in the detaileddescription are also possible. As previously described, the controlcircuit 14 may include the system controller 44 and one or more of thesystem control sensors 78, as well as a reference signal generator 82.The system controller 44 can be a programmable controller having amicroprocessor (not separately shown) that implements control algorithmsfor the control of the generator output, namely voltage and frequency.The system controller 44 controls the generator output by applying acontrol output signal 84 to the control valve assembly 42, directing thecontrol valve assembly 42 to meter fluid, and hence power, to the motor26 for driving the generator. The system controller 44 varies the powersupplied to the motor 26 through the use of the control output signal84. It should be appreciated that the control output signal 84 can be apulse-width modulated voltage waveform or a variable DC output voltageapplied to the solenoid 56 of the control valve assembly 42.

Vehicles today often rely on sensitive and delicate electronicsequipment, wherein only the cleanest of power is acceptable foroperation. Very little variance in the output frequency of an ACgenerator is tolerable in order to operate various devices such ascomputers and communications equipment. Merely close frequency output inrelation to desired frequency output is not good enough. Accordingly, itmay be desirable to compare actual frequency with a predeterminedfrequency, rather than merely relying on sensed motor speed as anindirect method of determining the generator's output characteristics.Of course, it is to be understood that sensing rotational speed of themotor 26 may be adequate in certain applications. Nonetheless, in oneembodiment, the electrical output 78 d can be electrically coupled tothe generator. The reference signal generator 82 can be in electricalcommunication with the system controller 44 and generates a referencesignal 86 indicative of the predetermined output frequency. The systemcontroller 44 may include a comparing sub-circuit 88 that implementscontrol algorithms for comparing sensed output frequency with thereference signal 86. The comparing sub-circuit 88 can then generate andtransmit control output signals for controlling the control valveassembly 42 such that the supply of fluid conducted to the motor 26 issufficient to maintain desired generator output frequency. Additionally,if the system controller 44 detects a load change, and hence a change inoutput voltage and frequency, the system controller's predictivesoftware algorithms can assist the generator in recovering to stableoperation more quickly than a purely reactive generator system.

Similarly, electrical devices often have very precise voltagerequirements wherein only the tightest voltage regulation is acceptable.Therefore, it may be advantageous for the system controller 44 to be inelectrical communication with a generator voltage regulator (not shown).The system controller 44 can monitor the electrical output via theoutput sensor 78 d and make adjustments using the generator voltageregulator resulting in very tightly controlled voltage. Additionally,the system controller 44 can anticipate and adjust the generator voltageregulator to promote system stability, especially during loadvariations, such as adjusting voltage to eliminate system oscillationand quickly recovering the desired voltage level following theapplication of an inductive load (e.g., starting a motor).

In one embodiment, the system controller 44 may also implementadditional control algorithms for the electrical or mechanical system'soutput functions in response to load variations, physical changes in theelectrical or mechanical system's operating environment or equipment,and communications from the user or other electronic modules. As theload on the electrical or mechanical system is increased or decreased,or the hydraulic fluid viscosity changes due to temperature fluctuationsand such, or the operating characteristics of the pump 16, motor 26, orcontrol valve assembly 42 change due to ambient conditions or wear, thesystem controller 44 can further adjust outputs to maintain consistentoperation of the electrical or mechanical system.

The control circuit 14 may include an operator interface module 90enabling an operator of system 10 to communicate with the systemcontroller 44 through a bi-directional asynchronous serialcommunications interface. The operator interface module 90 can displaysystem operating parameters through an information display 92. Asnon-limiting examples, the operating parameters displayed may includeoutput voltage, frequency, current, hydraulic fluid temperature, totaloperating hours, and the like. The operator interface module 90 can alsodisplay or announce alarm conditions or faults detected by the systemcontroller 44 and permit the operator to interact with the systemcontroller 44 and influence the operation of auxiliary power source 32.The alarm conditions can be announced by an audible alert 94 included inthe operator interface module 90. The operator may also influence theconfiguration of the system controller 44. For example, the operator mayturn the hydraulic control system 10 on or off through an ON/OFF switch96. Moreover, the operator may configure the system controller 44 toautomatically turn the auxiliary power source 32 on when sufficienthydraulic pressure is detected. Further, the operator can instruct thesystem controller 44 to purge air from the hydraulic lines, andconfigure the maximum expected output values to be controlled by thehydraulic control system 10. The operator communicates with the systemcontroller 44 through a keypad 98 disposed in the operator interfacemodule 90. It should be appreciated that multiple interface modules maybe linked together to add multiple operator interfaces if desired.

According to the control circuit 14 of the present invention illustratedin FIG. 2a , vehicle interface modules can be used by operators toperform all routine tasks or monitor any of the information availablethrough the operator interface module 90. Operation and diagnosticmonitoring of the generator can also be performed over commercialvehicle communications such as industry standard J-1939. The systemcontroller 44 broadcasts messages on the J-1939 vehicle bus, andmonitors the network for commands and requests for information.Additionally, personal computer (PC) and mobile device applications suchas tablets, pads, smart phones, etc., can be used to perform the samefunctions as the operator interface module 90 when connected to thesystem controller serial communications such as J-1939 communicationsbus. As illustrated in FIG. 2a , the communication may also be wirelessconnection such as Wi-Fi, wide area network (WAN), or a personal areanetwork (PAN) such as bluetooth, ZigBee, Z-Wave, IrDA, or the like. Inthis embodiment, the control circuit 14 includes a wireless device 99 ain communication with the operator interface module 90 and a wirelessdevice 99 b in communication with the system controller 44. The wirelessdevices 99 a and 99 b communicate with each other. It should beappreciated that the system controller 44 may contain electronicshardware support to communicate externally via any or all of theaforementioned protocols.

Referring again to FIG. 1 a, when the electrical or mechanical system tobe driven is idle or shut down, the valves 50 a and 50 b can be normallyclosed, directing all fluid flow into the bypass conduit 40, anddepriving the motor 26 of power. At the operator's request, through theoperator interface module 90, which communicates with the systemcontroller 44, the valves 50 a and 50 b can begin activating theelectrical or mechanical system by providing flow to the hydraulic motor26.

In another embodiment, the application of hydraulic pressure to thefluid circuit 22 may be interpreted by the system controller 44 as acommand to commence electrical or mechanical system operation. Theoperator may wish to configure the system controller 44 to automaticallypower the auxiliary power source 32 when the pump 16 is operating. Ifpressure sufficient for system operation is detected by the pressuresensor 78 a, system operation can automatically commence without furtherinstruction from the operator. On the other hand, if the hydraulicpressure falls below that required for system operation, the systemcontroller 44 can direct valve(s) 50, 50 a, 50 b to close fully,diverting all fluid flow into the bypass conduit 40, thereby shuttingdown operation of the motor 26.

The system controller 44 may further include a fluid pre-heatingsub-circuit 100. If the temperature sensor 78 b detects that hydraulicfluid in the hydraulic control system 10 is too cold for normaloperation, the system controller 44 can implement the fluid pre-heatingsub-circuit 100 to warm the fluid to a safe operating temperature. Thefluid pre-heating sub-circuit 100 can generate control output signalsfor controlling the control valve assembly 42 such that fluid bypassesthe motor 26 entirely until safe fluid operating temperature isobtained, avoiding damage to the mechanical components. The systemcontroller 44 can hold the valve(s) 50, 50 a, 50 b fully closed tocirculate the hydraulic fluid through the bypass conduit 40. Normalmechanical friction will warm the fluid until it reaches a firstpredetermined temperature, at which point the valve 50, 50 a, 50 b canbe opened only enough to pass the warming fluid slowly through the motor26. It should be appreciated that normal mechanical friction will warmthe fluid further until it reaches a second predetermined temperature,at which point full power operation can commence.

Further, if the temperature sensor 78 b detects the hydraulic fluid istoo cold for any operation, the system controller 44 can implement anauxiliary heater 131 (see FIG. 12) disposed within the hydraulic circuit12 in front of the inlet 18 of the pump 16. The auxiliary heater 131 canhave any number of power sources, AC power, DC power, diesel power, orpropane power. It should be appreciated that multiple sources of energyare possible to preheat the hydraulic fluid.

The application of the fluid pre-heating sub-circuit 100 can beincredibly advantageous in extremely low temperatures where thehydraulic fluid can partially congeal. If fluid were permitted to passthrough the motor 26 immediately, prior to frictional warming throughthe bypass conduit 40, lumps of congealed fluid can momentarily obstructthe motor gears causing the motor 26 to briefly decelerate and thenaccelerate. The deceleration and acceleration caused by lumps in thefluid passing through the motor gears occurs almost instantaneously,resulting in large voltage spikes at the output of the auxiliary powersource 32 (in the case of a generator). The duration of the voltagespike is very abrupt and the magnitude of the voltage spike can besufficient to damage various electrical loads. The fluid pre-heatsub-circuit 100 substantially minimizes this occurrence reducingwarranty claims and the costs associated with, while greatly increasingcustomer satisfaction and goodwill.

Once pressure and temperature are sufficient, full system operation canbegin. In order to bring the hydraulic control system 10 up to power,the system controller 44 may utilize a pulse width modulation (PWM)output control circuit to control power delivered to the valve(s) 50, 50a, 50 b, hence fluid delivered to the hydraulic motor 26. The duty cycleof the PWM outputs(s) can be gradually modified so the valve(s) 50, 50a, 50 b apply fluid to the hydraulic motor 26 in a controlled manner.This gradual application of power allows the hydraulic control system 10to gently overcome inertial effects, greatly reducing wear andincreasing system component lifetimes. During operation, the PWM canhave a dither, or noise added intentionally to the signal to prevent thevalve(s) 50, 50 a, 50 b from sticking if the control signal is static.It should be appreciated that forces to overcome a partially stuck valveare greater than that of one that is continually in motion and can causeminor instability. It should also be appreciated that the dither addedto the PWM can help prevent the valve(s) 50, 50 a, 50 b from stickingand increase system stability due to valve position movability remainingfairly constant.

Referring now to FIG. 4, a graphical representation of cold startoperation parameters of the hydraulic control system 10, utilizing thefluid pre-heating sub-circuit 100 and the power ramping PWM controlcircuit is illustrated. Pump speed 101 generally depicts revolutions perminute (RPMs) of the pump 16 over time at initial system coldtemperature start-up. The pump speed 101 can fluctuate over time as thevehicle engine speed fluctuates. Fluid temperature 103 generally depictstemperature of the fluid in the fluid circuit 22 during cold startoperation. At cold start, hydraulic fluid can bypass the motor 26 untilit warms to a sufficient temperature, at which point fluid is slowlydiverted to the motor 26 to gradually supply power to the hydrauliccontrol system 10. Also at cold start, hydraulic fluid can bypass thefluid cooler 70 by the use of an electronically controlled valve or amechanical pressure relief valve until the fluid warms to a temperaturerequiring cooling, at which point fluid flow gradually resumesproportional to fluid temperature through the fluid cooler 70. Further,during cold start operation, hydraulic fluid flow can be entirelyblocked by the closure of the valve 50, 50 a, 50 b wherein the fluidtemperature can rise within the pump 16 until a sufficient temperatureis reached, at which point fluid flow can resume proportional to fluidtemperature by the gradual opening of the valve(s) 50, 50 a, 50 b.During this ramp-up, fluid temperature 103 can increase furtherpermitting full system operation to begin. Motor speed 105 generallydepicts operation of the motor 26 (in RPMs) during cold start. The motor26 can get little or no power, while the fluid warms as it circulatesthrough the bypass conduit 40. Once a desired temperature is obtained,the motor speed 105 slowly ramps up as fluid is gradually supplied tothe motor 26. Once full system operation commences, the motor speed 105remains substantially constant, despite fluctuations in engine speed andhence the pump speed 101.

Further, the system controller 44 may include over-temperature shut-downcontrol measures. When the temperature of the hydraulic fluid exceedssafe operating conditions, the system controller 44 can notify theoperator of the electrical or mechanical system that excessivetemperatures are being detected, and action may be required to preventdamage to the hydraulic control system 10. When the temperature exceedsyet another temperature threshold, the system controller 44 can start aninternal timer. If the timer expires, the valve 50, 50 a, 50 b may befully closed by the system controller 44, bypassing all fluid flow andshutting down the hydraulic control system 10 unless the operator issuesan emergency override instruction through the keypad 98, or otheroptional interface to prevent the shutdown and keep the electrical ormechanical system operating.

Further, the system controller 44 may include a PWM sub-circuit tocontrol a fan in proximity with the auxiliary power source 32 to coolthe auxiliary power source 32. The auxiliary power source 32 may also becooled by a suitable liquid cooled by an external fluid cooler.

Further, the hydraulic control system 10 may include an air filter toprotect key components, primarily the auxiliary power source 32, fromforeign contaminants. A sensor associated with the air filter todetermine when the air filter is clogged or otherwise needs replacingmay be electrically coupled to the system controller 44.

The system controller 44 may further include a means of enabling ordisabling the primary power source 24 such as disabling the power takeoff (PTO) via a primary power source control. In one embodiment, thesystem controller 44 may be configured to disable the primary powersource 24 to prevent damage to the hydraulic control system 10 such aswhen the system operating temperature exceeds a predetermined limit. Inanother embodiment, the system controller 44 may be configured to notallow the primary power source 24 to be enabled when conditions are suchthat damage to the hydraulic control system 10 or an operator couldoccur.

The system controller 44 may also have the ability to record allabnormal conditions and faults to a diagnostic memory 106. The faultscan be retrieved from the diagnostic memory 106 by an operator anddisplayed by the operator interface module 90, or any aforementionedcommunication methods, to evaluate the conditions seen by the hydrauliccontrol system 10 and assist in any necessary troubleshooting. Recordedconditions may include, but are not limited to, valve voltage faults,valve current faults, over current faults, current sensing faults,temperature sensing faults, ground faults, number of over temperatureoverrides, fan faults, voltage sensing faults, hours run with overtemperature, highest recorded frequency, highest recorded voltage,highest measured current, highest measured temperature, hours run withovercurrent, hours on oil filter, calibration values, maximum currentvalues, and total hours.

Yet another advantage of the hydraulic control system 10 is that it canbe a self-contained system that can be readily plugged into externalhydraulic and electrical connections, or retrofit to a vehicle having apower take-off, engine driven belt drive, or any other power supplysource. Moreover, the hydraulic control system 10 may include a circuitbreaker 108 as yet another protective feature. The circuit breaker 108may be located in series with the output conductors 80 connected tooutput terminals of the auxiliary power source 32. It should beappreciated that the circuit breaker 108 can operate conventionally byopening an external circuit (not shown), which is connected to theconductors 80 to conduct electrical power to powered equipment.

The circuit breaker 108 may be remotely trip-able. The system controller44 or a standalone electronic sub-circuit (not shown) may be used tomonitor the generator output current and determine if the circuitbreaker 108 should be tripped. In one embodiment, custom trippingprofiles may be created to meet application specific requirements. Inanother embodiment, electrically controlled contacts (not shown)controlled by the system controller 44 or a standalone electronicsub-circuit may be substituted for the circuit breaker 108. As anothersafety feature, sensors can be added to the hydraulic control system 10allowing the system controller 44 to detect if a cover or door (notshown), which is to protect a user from high voltages, is opened. Inturn, the auxiliary power source 32 can be disabled by opening thecircuit breaker 108 or opening the electrically controlled contacts.

The hydraulic control system 10 can contain an electrical sub-circuit toshut down user prioritized loads dependent upon system conditions suchas overheating and resources such as inadequate source power. Thehydraulic control system 10 can then communicate to a user the abilityto return loads to power as the system conditions allow.

The hydraulic control system 10 can have a means of troubleshootingwherein the system controller 44 contains an electrical sub-circuitcontaining the ability to manually control the valve assembly 42 and/orcooling fan 72.

A general overview of the operation of the hydraulic control system 10,according to an embodiment, is provided below. The system controller 44can sense adequate operating pressure in the fluid circuit 22. If thesystem controller 44 does not automatically interpret sufficientpressure as a command to commence operation, it can wait to receive acommand signal from an input, operator, or other electronic module toactivate the hydraulically powered mechanical or electrical system. Thesystem controller 44 can then check the status and values of the controlinputs to ensure operation will be safe and effective. If the hydraulicfluid temperature is too low, the fluid pre-heat sub-circuit 100 cancause the fluid to warm to safe operating temperatures. The systemcontroller 44 can then gradually apply power to the motor 26 by slowlyopening the valve(s) 50, 50 a, 50 b, according to power ramping PWMcontrol algorithms. Appropriate control signals can be applied by thesystem controller 44 to outputs in response to the control inputs toachieve the desired control and function of the hydraulic control system10. If the hydraulic fluid temperature becomes too high for safeoperation, over-temperature shut-down can be implemented to shut downthe operation of the electrical or mechanical system. In one embodiment,the system's operating parameters may be sent via serial communicationsusing a proprietary protocol to the operator interface module 90 orother electronic module utilizing standard protocols for J-1939 andWLAN. In another embodiment, the system's operating parameters may besent via a standard communication protocol to the vehicle data bus.Further, the operator interface module 90 can communicate with thesystem controller 44 using the vehicle data bus. If a command isreceived from an operator or other electronic module to cease operation,or the hydraulic pressure falls below that required for operation, thesystem controller 44 can shut down the electrical or mechanical systemby fully closing the valve(s) 50, 50 a, 50 b, bypassing all hydraulicfluid flow to the motor 26.

Yet another embodiment of the hydraulic control system 10 is illustratedin FIG. 5. A hydraulic control system 110 is similar to the hydrauliccontrol system 10 described with reference to FIG. 1, however ratherthan using the control valve assembly 42 to regulate the amount of theoutput of the pump 16 that passes through the motor 26, a variabledisplacement pump 112 is utilized which has an external input whichenables the control circuit 14 to vary the pump displacement to achievethe desired flow rate needed for the motor 26. The control circuit 114of the FIG. 5 embodiment is otherwise generally similar to the controlcircuit 14 utilized in the FIG. 1 embodiment and like componentsfunction in a similar manner as described previously.

In operation, the output from the pump 112 provides hydraulic fluid tothe motor 26. As previously described, the control valve assembly 42utilized in the FIG. 1 embodiment is no longer required provided thepump minimum displacement is sufficiently low. If the minimum pumpdisplacement is substantial, i.e., over 20% of maximum pumpdisplacement, the control valve assembly 42 as previously described canbe added in order to deactivate the motor 26 at desired times. When thecontrol valve assembly 42 is not used, an optional pressure regulator116 can be provided to maintain desired minimum back pressure on theoutlet of the pump 112 which is sufficient to operate a pumpdisplacement control 120 which is supplied with hydraulic fluid via line118.

The pump displacement control 120 cooperates with the pump 112 to varythe displacement of the pump 112 as needed. The pump displacementcontrol 120 can have a hydraulic output or alternatively a mechanicaloutput as dictated by the pump design. The pump displacement control 120varies the pump displacement as a function of a control signal 84received from the system controller 44 illustrated in FIG. 2. In oneembodiment, the pump displacement control 120 is hydraulically powered,and in another embodiment, an electrically operated actuator such as astepper motor could be used to vary pump displacement. The hydrauliccontrol system 110 of the FIG. 5 embodiment is designed to have reducedpumping losses and associated energy consumption when compared to thehydraulic control system 10 of FIG. 1 in which high pressure fluid isroutinely bypassed about the motor 26 at high pump speed conditions.

FIGS. 6 and 8 illustrate one embodiment of a packaging module 122 formounting the hydraulic control system 10 of the present invention to amotor vehicle. The illustrations of module 122 in FIGS. 6 and 8 are atopposite orientations.

Typically, there this insufficient space in the vehicle enginecompartment or adjacent the vehicle drive train to mount a hydraulicmotor and associated generator inside the vehicle body. The module 122is suitable for attachment to an exterior of the vehicle. A largeportion of the hydraulic control system 10 can be mounted within themodule 122. The portion of the hydraulic control system 10 suitable formounting outside the module 122 is illustrated in phantom outline inFIG. 5 by reference number 124. In one embodiment, the variabledisplacement pump 112 and associated pump displacement control 120 willbe mounted directly to the primary power source such as internalcombustion engine or a power takeoff associated with an internalcombustion engine of the vehicle. The motor 26 and the auxiliary powersource 32 are mounted externally in the module 122 as are the othercomponents identified in portion 124 of FIG. 5.

The module 122 when mounted external to the vehicle not only eliminatesspace problems but further facilitates dissipating any excess heatgenerated by the pump 112, motor 26, and auxiliary power source 32 viathe fluid cooler 70. The module 122 may be configured to direct coolingair through the fluid cooler 70 in an upward or downward direction toprovide efficient cooling and to reduce mounting space requirements. Themodule 122 can be provided with an open grate top 126 (labeled in FIG.8) which allows air to freely circulate and exhaust through the module122 and provides a non-slip working surface for the system user. In oneembodiment, the module 122 has the cooling fan 72 forcing cooling airabout the system components. The module 122 may also include a baffle(not shown) to separate cooler intake air from mixing with warmerexhausted air. The fluid circuit supply and discharge hydraulic conduitscan be disposed to exit the hydraulic control system 10 in a generallydownward direction in relation to the system mounting orientation toprovide reduced mounting space requirements.

The fluid cooler 70 can be disposed within a closed tolerance enclosure125 also containing the cooling fan 72. The tolerance enclosure 125 cangenerally provide a more even airflow throughout the surface of thefluid cooler 70 in order to increase cooler efficiency.

As indicated, the motor 26 and the auxiliary power source 32 (i.e.,generator) of the hydraulic control system 10 are mounted within themodule 122. As described in further detail below with reference to FIGS.9, 10, and 11, the hydraulic control system 10 may include a secondaryauxiliary power source 129. The secondary auxiliary power source 129 maybe serially connected to the auxiliary power source 32 (as shown in FIG.9), in parallel with the auxiliary power source 32 and connected to theshaft 34 of the motor 26 (as shown in FIG. 10), or serially connected tothe motor 26 via a shaft separate from the shaft 34 (as shown in FIG.11). For instance, as illustrated in FIG. 8, the hydraulic controlsystem 10 mounted within the module 122 includes the secondary auxiliarypower source 129, in the form of a pump for hydraulic extractionequipment, which is serially connected to the auxiliary power source 32and extends out of the module 122.

Referring to FIG. 7, the hydraulic control system 10 can be configuredwith the cooler 70 and the fan 72 contained together in a cooler/fanassembly 127. The cooler/fan assembly 127 can be positioned to open airwhen the hydraulic control system 10 is being operated or can berepositioned adjacent to enclosure 128 to create a space saving module130. The repositioning of the cooler/fan assembly 127 can beaccomplished by using hinges, slides, rollers, or any similar method. Toincrease cooling efficiency, an auxiliary fan (not shown) may bepositioned within the enclosure 128 to ensure proper cooling of theauxiliary power source 32. In addition, a position sensor (not shown)can be added in communication with the system controller 44 wherein theposition of the cooler 70 can be determined in that if the cooler 70 isin the storage position, the hydraulic control system 10 will notfunction. Further, a temperature sensor may be disposed on or near theauxiliary power source 32 and be in electrical communication with thesystem controller 44. The system controller 44 may contain an electricalsub-circuit to monitor the temperature and shut down the hydrauliccontrol system 10 if predetermined unsafe conditions exist.

The enclosure 128 may contain interlocks in communication with thesystem controller 44 to determine if electrical connections are exposedto an operator or if the cooler/fan assembly 127 is folded out andunsafe for travel. The enclosure 128 can be capable of withstandingwater immersion for use with various requirements of vehicles thehydraulic control system 10 may be installed on.

The hydraulic control system 10 may have other features. For instance,the system controller 44 may control a voltage regulator (not shown) forthe auxiliary power source 32 using the output of the auxiliary powersource 32 or another source of AC or DC power. The hydraulic controlsystem 10 may output multiple types of power simultaneously, such as DCpower or 60 Hz, 50 Hz and 400 Hz AC power. It should be appreciated thatthere are many combinations of power possible and the combinationslisted are merely exemplary. It should also be appreciated that theauxiliary power source 32 can be any device requiring or preferring moreenvironmental protection than can be offered where the primary powersource 24 is located and, in the case of a typical engine drivenvehicle, the power available is located at external hydraulic andelectrical connections or at a vehicle's power take-off.

Referring now to FIGS. 9, 10, and 11, with continued reference to FIG.1, additional embodiments of the hydraulic control system 10 areillustrated. The hydraulic control system 10 shown in each of FIGS. 9,10, and 11 embodiments is the same as hydraulic control system 10described with reference to FIGS. 1 and 2 with the exception that thesecondary auxiliary power source 129 is employed in addition to theauxiliary power source 32. That is, the hydraulic control system 10 hasthe ability to include two or more auxiliary power sources. Theauxiliary power sources 32 and 129 can be coupled together serially orin parallel. In FIG. 9, the secondary auxiliary power source 129 isserially connected to the auxiliary power source 32. In FIG. 10, thesecondary auxiliary power source 129 is in parallel with the auxiliarypower source 32 and is connected to the shaft 34 of the motor 26. InFIG. 11, the secondary auxiliary power source 129 is serially connectedto the motor 26 via a shaft separate from the shaft 34. The auxiliarypower sources 32 and 129 may be drivably connected to a clutch or otherconnection and disconnection apparatus to independently controlfunctionality. Further, if one or more auxiliary power sources 32 and129 require a different rotational speed, then they may be drivablyconnected to an under-drive or over-drive device such as a gear box, abelt drive, or a chain system.

Referring now to FIG. 12, with continued reference to FIG. 1, a stillfurther embodiment of the hydraulic control system 10 is illustrated.The hydraulic control system 10 shown in FIG. 12 is the same ashydraulic control system 10 described with reference to FIG. 1 with theexception that one or more additional control valve assemblies 131, 132are employed. For instance, the hydraulic control system 10 may includea control valve assembly 132 disposed serially and/or parallel withrespect to the supply conduit 36 such that it is interposed between theoutlet 20 of the pump 16 and the control valve assembly 42. The controlvalve assembly 132 may be employed to warm and/or isolate and protectthe rest of the hydraulic control system 10 from conditions existing atthe pump 16 such as cold hydraulic fluid. The control valve assembly 132may be slowly opened to allow fluid to propagate to the rest of thehydraulic control system 10 as conditions improve such as the hydraulicfluid warming to an appropriate temperature.

The present invention has been described in an illustrative manner. Itis to be understood that the terminology, which has been used, isintended to be in the nature of words of description rather than oflimitation.

Many modifications and variations of the present invention are possiblein light of the above teachings. Therefore, the present invention may bepracticed other than as specifically described.

What is claimed is:
 1. A hydraulic control system comprising: a variabledisplacement hydraulic pump drivably connectable to a primary powersource, said pump having an inlet to receive fluid and an outlet todischarge fluid under pressure; a hydraulic motor having an inlet toreceive fluid under pressure and an outlet to discharge spent fluid,said motor being drivably connectable to an auxiliary power source; afluid circuit including a supply conduit to fluidly communicate withsaid outlet of said pump and said inlet of said motor, said supplyconduit including a valve supply conduit portion and a motor supplyconduit portion to conduct fluid discharged by said pump to said motorand a return conduit to fluidly communicate with said outlet of saidmotor and said inlet of said pump, said return conduit to return fluiddischarged by said motor to said pump; a control valve assembly disposedin said supply conduit to fluidly communicate between and with said pumpand said motor; a control circuit in communication with said controlvalve assembly to control the pump output such that said motor is drivenat a constant rotational speed to thereby drive the auxiliary powersource at a constant rotational speed despite fluctuations in rotationalspeed of the primary power source; said control valve assembly includingat least two proportional valves disposed in parallel between said valvesupply conduit portion and said motor supply conduit portion to controla rotational speed of said motor, wherein one of said at least twoproportional valves is a first valve providing coarser flow controlresolution and another of said at least two proportional valves is asecond valve smaller than said first valve providing finer flow controlresolution; and said control circuit including a system controller incommunication with said control valve assembly to provide a pulse widthmodulation (PWM) output control signal to control power delivered tosaid at least two proportional valves.
 2. The hydraulic control systemas set forth in claim 1 wherein said at least two proportional valvesare of a normally closed type.
 3. The hydraulic control system as setforth in claim 1 wherein said second valve is smaller in size than saidfirst valve.
 4. The hydraulic control system as set forth in claim 1wherein said fluid circuit includes a hydraulic fluid cooler disposedserially with respect to said return conduit, an electrically operatedfan disposed adjacent said fluid cooler to pass ambient air through saidfluid cooler, and a thermostat disposed proximate to said fluid coolerto operate said fan when fluid contained within said fluid coolerattains temperatures exceeding a predetermined temperature.
 5. Thehydraulic control system as set forth in claim 4 wherein said fluidcircuit includes a hydraulic fluid filter disposed serially with respectto said return conduit.
 6. The hydraulic control system as set forth inclaim 1 wherein said fluid circuit includes a hydraulic fluid coolerdisposed serially with respect to said return conduit and a fan disposedadjacent said fluid cooler to pass ambient air through said fluidcooler, wherein said fan is hydraulically operated by said fluidcircuit.
 7. The hydraulic control system as set forth in claim 1including an interface module having a display in electricalcommunication with said control circuit to display real time systemoperating characteristics to an operator.
 8. The hydraulic controlsystem as set forth in claim 7 wherein said display device is a smartphone.
 9. The hydraulic control system as set forth in claim 7 whereinsaid display device is a tablet.
 10. The hydraulic control system as setforth in claim 7 wherein said display device is a personal computer. 11.The hydraulic control system as set forth in claim 7 wherein saidinterface module displays fault and alarm conditions.
 12. The hydrauliccontrol system as set forth in claim 7 wherein said system controllersends system operating parameters via serial communications usingprotocols to said interface module.
 13. The hydraulic control system asset forth in claim 12 wherein said protocols for said interface moduleare standard protocols for J-1939 and WLAN.
 14. The hydraulic controlsystem as set forth in claim 7 wherein said system controller sendssystem operating parameters via a standard communication protocol to avehicle data bus.
 15. The hydraulic control system as set forth in claim1 wherein said fluid circuit further includes a fluid reservoir and afluid level sensor disposed in said fluid reservoir to generate a fluidlevel fault when the fluid level falls below a first minimum fluid leveland to generate a control signal shutting down said system when thefluid level falls below a second minimum level.
 16. The hydrauliccontrol system as set forth in claim 1 wherein said pump is operable todrive another auxilliary device in addition to said motor.
 17. The Ahydraulic control system as set forth in claim 1 wherein said fluidcircuit includes a fluid reservoir and a venturi boost to draw fluidfrom the fluid reservoir into said fluid circuit.
 18. The hydrauliccontrol system as set forth in claim 1 wherein said fluid circuitincludes a fluid reservoir and a charge pump to draw fluid from saidfluid reservoir into said fluid circuit.
 19. The hydraulic controlsystem as set forth in claim 1 wherein said fluid circuit includes ahydraulic fluid filter disposed serially with respect to said returnconduit.
 20. The hydraulic control system as set forth in claim 1including a heater disposed in thermal communication with the fluid toaid in cold operation and startup.
 21. The hydraulic control system asset forth in claim 1 including a remote tripable breaker or otherappropriate contacts electrically coupled to the control circuit todisconnect an output of the auxiliary power source.
 22. The hydrauliccontrol system as set forth in claim 1 wherein said control circuitincludes an electrical output sensor coupled to a generator fordetermining output voltage of the generator, a reference signalgenerator to generate a reference signal indicative of a predeterminedoutput voltage, and a comparing sub-circuit to compare sensed outputvoltage with the reference signal and to generate a control signal tocontrol the pump output such that the supply of fluid conducted to saidmotor is sufficient for the generator to maintain desired outputvoltage.
 23. A hydraulic control system comprising: a variabledisplacement hydraulic pump drivably connectable to a primary powersource, said pump having an inlet for receiving fluid and an outlet fordischarging fluid under pressure; a hydraulic motor having an inlet toreceive fluid under pressure and an outlet to discharge spent fluid,said motor being drivably connectable to an auxiliary power source; afluid circuit including a supply conduit to fluidly communicate withsaid outlet of said pump and said inlet of said motor, said supplyconduit including a valve supply conduit portion and a motor supplyconduit portion to conduct fluid discharged by said pump to said motorand a return conduit to fluidly communicate with said outlet of saidmotor and said inlet of said pump, said return conduit to return fluiddischarged by said motor to said pump; a control valve assembly disposedin said supply conduit to fluidly communicate between and with said pumpand said motor; a control circuit in communication with said controlvalve assembly to control the pump output such that said motor is drivenat a constant rotational speed to thereby drive the auxiliary powersource at a constant rotational speed despite fluctuations in rotationalspeed of the primary power source; an interface module having a displayin communication with said control circuit to display real time systemoperating characteristics to an operator and a wireless communicationconnection between said display device and said control circuit; saidcontrol valve assembly including at least two proportional valvesdisposed in parallel between said valve supply conduit portion and saidmotor supply conduit portion to control a rotational speed of saidmotor, wherein one of said at least two proportional valves is a firstvalve providing coarser flow control resolution and another of said atleast two proportional valves is a second valve smaller than said firstvalve providing finer flow control resolution; and said control circuitincluding a system controller in communication with said control valveassembly to provide a pulse width modulation (PWM) output control signalto control power delivered to said at least two proportional valves. 24.The hydraulic control system as set forth in claim 23 wherein saiddisplay device is a smart phone.
 25. The hydraulic control system as setforth in claim 23 wherein said display device is a tablet.
 26. Thehydraulic control system as set forth in claim 23 wherein said displaydevice is a personal computer.
 27. The hydraulic control system as setforth in claim 23 wherein said wireless communication connectionincludes a wireless device in communication with said display and awireless device in communication with said control circuit.
 28. Thehydraulic control system as set forth in claim 23 wherein said at leasttwo proportional valves are of a normally closed type.
 29. The hydrauliccontrol system as set forth in claim 23 wherein said second valve issmaller in size than said first valve.
 30. The hydraulic control systemas set forth in claim 23 wherein said system controller sends systemoperating parameters via serial communications using protocols to saidinterface module.
 31. The hydraulic control system as set forth in claim30 wherein said protocols for said interface module are standardprotocols for J-1939and WLAN.
 32. The hydraulic control system as setforth in claim 23 wherein said system controller sends system operatingparameters via a standard communication protocol to a vehicle data bus.